Even if you invent some kind of automated Nazi detector
As interesting a problem as this might be (my final year undergrad project was similar in nature), the nuance of written word can be significant and difficult to detect. Making a good product and then ensuring multiple communities would adopt it is not realistic in 2023.
What is realistic, however, is a zero tolerance policy against such individuals. What we should be doing is ostracizing them. You take away their platform, you take away their power. They can only do so much damage if they're all gathered up in a single community with no ties or influence to the rest of the world.
Why give them a platform and an audience to begin with? They're the scum of the earth. Fuck them.